These projects are directed towards a greater understanding of the quaternary organization of plasma lipoproteins and of the function of the oligomeric species involved in the transport and metabolism of lipids in plasma. The apolipoprotein composition of plasma lipoproteins in viewed as the governing factor in directing lipoprotein metabolism. Specificity is believed to be related directly to apolipoprotein secondary, tertiary and quatenary structure. Studies of the hydrodynamic properties of apolipoproteins have been extended to include apoH and the mixed interaction between two self-associating apolipoproteins, apoA-I and apoC-I. A method of analyzing irreversible ligand-cell interactions has been developed and applied to plasma lipoprotein cell interactions. The molecular properties of radiolabeled apoA-I have also been evaluated. A knowledge of the molecular properties of the specific self-associated and mixed-associated oligomeric apolipoprotein complexes (modified and native) are of major importance to our ultimate understanding of plasma lipoprotein metabolism.